1. Technical Field
This disclosure concerns a way to efficiently, economically and safely increase the highway vehicle flow rate of passenger vehicles per highway lane per hour. In particular, this disclosure relates to a vehicle transporter system that provides a way to quickly and efficiently load and unload driver occupied passenger vehicles on and off of a vehicle transporter and safely transport the driver occupied passenger vehicles.
2. Background Information
Traffic congestion, both in the U.S. and around the world, continues to increase because the number of vehicles on roadways, arterials, and streets and roads continues to increase as population and wealth increase, and as annual miles traveled per vehicle increase due to the spread of cities outward and other demographic, economic and social factors. In the U.S., as well as in many other nations, congestion for several decades has continued to increase because the rate at which highway capacity is constructed remains significantly below the rate of growth in highway vehicle miles traveled. As a result, more and more vehicles attempt to utilize highway capacities intended to support one-third or one-fourth of today's traffic demands. Long-range U.S. Department of Transportation (USDOT) databases indicate that statistics for the years 1980 to 2003 for annual vehicle miles traveled steadily increased at approximately 4.0% per year, but highway capacity increased only about 1.4% per year.
There are at least three fundamental variables that affect roadway traffic flow: 1) traffic in-flow capacity; 2) roadway segment design capacity; and 3) traffic out-flow capacity. Traffic in-flow capacity determines the number of vehicles flowing into a given roadway segment. If the number of vehicles flowing into the segment is low in relation to the capacity of the segment, then traffic density on the segment will be low. Traffic normally flows near, or even above, the maximum intended speed and traffic congestion is less likely to occur. If the number of vehicles flowing into the segment for a given period of time is higher than the segment can accommodate for that period of time, then traffic backs up onto the roads and streets. Such back ups cause traffic jams on the feeder roads and streets, and on the given segment and upstream of the feeder roads and streets. The traffic flow of feeder roads that route traffic into a roadway segment is a determining factor as to the amount of traffic that may utilize the roadway segment.
Roadway segment design capacity generally determines the intended traffic capacity of the roadway segment. The number of lanes of the roadway segment and associated structures (e.g., on-ramps, off-ramps, traffic signals, interchanges and intersections) are built with the intention of accommodating expected and forecasted traffic demand, given budget constraints, physical limitations (e.g., natural features such as mountains, rivers and lakes) and the presence of the human-built environments (e.g., cities, industrial zones, neighborhoods, and transportation facilities such as railways and airports).
Current road design technology affords a maximum sustainable per lane traffic capacity for a nominal, well-designed roadway lane of about 2,000 to 2,200 passenger cars per lane per hour assuming good, daylight driving conditions and no disruptive conditions or events. Vehicles larger than passenger cars that occupy more roadway space per vehicle than standard passenger cars are considered by traffic engineers and roadway designers in terms of “passenger-car-equivalents”. For example, a large freight truck may be assigned a “passenger-car-equivalence” of 3 passenger cars. A four-lane roadway nominally has a maximum capacity in the range of 8,000 to 8,800 cars per hour equivalent to 2,000 to 2,200 cars per lane per hour. Experience and numerous empirical and theoretical traffic flow studies provide comprehensive evidence that when traffic flows exceed 2,000 to 2,200 cars per lane per hour, traffic flows become progressively unstable and unsustainable. This instability is due to random variations in vehicle spacing, driver skills and performance, and a reduction in the available time to perform particular traffic maneuvers and spacing between vehicles that prevent a driver from performing the traffic maneuvers. As traffic flows increase above the range of 2,000 to 2,200 cars per lane per hour, traffic then becomes increasingly subject to chaotic break down from smooth, high-speed traffic flows into stop and start very low-speed, traffic jams. During such traffic jams, vehicles are characteristically very closely spaced with separations between vehicles at ten to twenty foot intervals from the front bumper of one vehicle to the rear bumper of the next vehicle. Such traffic jams typically result in traffic flows decreasing to 1,000 passenger cars per lane per hour, or even less.
Traffic outflow capacity (e.g., the maximum number of vehicles that can leave a roadway segment per hour) depends on the traffic capacity and temporal traffic condition of roadway exits and outbound interchanges. If the traffic capacity of exit roadways is too low, and/or if traffic on the roadway exits is not flowing at or below outflow capacity of those roadway exits, then traffic attempting to exit onto the exit roadway backs up onto the roadway segment feeding the exit roadway, which causes delays, slow and/or chaotic traffic flow, and breakdown into persistent very low flow, jammed conditions.
Other factors that may impact traffic flows and/or render traffic conditions problematic include: visibility; weather conditions; accidents and incidents; stochastic effects; erratic and abnormal driver behavior; public safety traffic; construction zones; and special events. Driving under conditions of darkness, or any lighting condition less favorable than normal daytime lighting, decreases driver performance and suppresses traffic flows. Adverse weather depresses traffic flows, including snow, rain, icing or hydroplaning road conditions, high winds and gusts. Adverse weather conditions create driving dangers that require slower speeds and create fundamentally unpredictable chaotic conditions that depress traffic flows. Traffic accidents may block one or more lanes for unknown amounts of time, depending upon the severity of the accident and the degree of emergency vehicle access to the accident scene. Similarly, vehicles suffering flat tires or mechanical problems may block or disrupt traffic until the affected vehicle is repaired or removed. According to USDOT, traffic accidents and incidents cause approximately 25 percent of all congestion. Each minute of lane blockage creates about four minutes of congestion after the incident is cleared. USDOT indicates that the best performing state transportation agencies clear traffic accidents and incidents within approximately 22 minutes of on-scene arrival, which suggests that in zones subject to persistent congestion, accidents and incidents may create more than 1.5 hours of congestion on average.
Traffic congestion may be explained by the stochastic effects of traffic congestion that occurs due to any number of reasons, and results in traffic slowing and throughput of vehicles diminishing. On a road segment operating at or near its sustainable capacity, the start of congestion may create a vicious cycle effect in which minor congestion creates more congestion, and so on, until the segment is in a bumper to bumper, stop and go jam. A traffic accident may result in “rubber-necking” as drivers moving past the accident slow down more than needed, or for longer than needed, in order to satisfy their curiosity. In such conditions congested zones may lengthen toward the traffic input facilities of the segment because the capacity-level inputs, or near capacity-level inputs continue to feed traffic into the jam. Public safety traffic (e.g., emergency vehicles) moving at high speed and having legal lane priority cause flow disruptions and suppress traffic throughput. Highway arrests for traffic violations cause traffic suppression effects similar to accidents and incidents. Erratic and/or abnormal drivers (e.g., drivers driving at either abnormally high or abnormally low speeds and/or drivers weaving from lane to lane) disrupt normal traffic and suppress throughput. Impaired, inattentive drivers and drivers otherwise unable to control their vehicles force normal drivers to adjust their driving in ways that disrupt free flow traffic.
Construction zones for highway construction and/or rehabilitation projects commonly remove one or more lanes of capacity from highways thereby reducing traffic throughput and frequently causing severe traffic congestion. USDOT estimates that construction zones account for approximately ten percent of all U.S. traffic congestion. Special events (e.g., athletic, entertainment events, and annual holidays) create surges of traffic that may cause traffic demand levels to exceed available traffic capacity with regard to input capacity, segment design capacity and/or outflow capacity.
Some experts conclude that in developed societies like the United States, the most practical roadway paths have already been put into highway use, and the growth of surrounding urban development and physical constraints (e.g., geographical and environmental) make expansion of existing roadways and/or construction of new roadways too expensive to be practical. The addition of roadway capacity may also be legally constrained by environmental laws, successful environmental lawsuits, and/or the political action of highway opponents. Furthermore, there have been periods in recent U.S. history when funds collected for the stated purpose of highway construction and maintenance have been withheld by the federal government and made unavailable to states, counties and cities for highway capacity maintenance and expansion.
Many highway experts consider urban/suburban highway capacity expansion by the conventional means of adding new lane miles to existing roadway systems in amounts sufficient to resolve congestion (e.g., an estimated doubling and/or tripling of highway capacity) impossible, as a practical matter, because of space constraints, budget limitations, legal and political realities. In the future, more and more critical highways may be expected to show multiple factor capacity deficiencies as populations increase and highway travel demands rise accordingly.
Addressing the deficiency of highway capacity in urban/suburban settings is further complicated by empirical limitations demonstrated by currently available or reasonably foreseeable technologies that address highway congestion. These technologies are, for the most part, intended to make highways run more efficiently, or to reduce the frequency of events that create congestion. Current congestion reduction methods and technologies primarily operate within the long-standing optimum throughput band of approximately 2,000 to 2,200 passenger cars per lane per hour. The intended effect of these technologies is to sustain these flow levels and prevent, to the extent possible, events that create congestion and reduce vehicle flows substantially below the 2,000 to 2,200 cars per lane per hour level.
Some traffic congestion programs (e.g., transit systems, organized van pools, and variable highway toll programs) are intended in part or in whole to reduce the number of vehicles present on urban/suburban highways, especially during peak traffic demand periods. These efforts have proved to have only nominal success in most settings as evidenced by the following considerations: 1) highway vehicle miles traveled per year continues a steady compound annual rise of approximately 4%; 2) despite a sharply increased investment in transit systems all across the U.S., transit systems produce 1.5% percent of U.S. urban/suburban passenger miles; and 3) the annual urban/suburban passenger miles produced by transit systems has declined since 1970 from a 3.63% share to a 1.5% share in 2005. The annual highway congestion indices compiled by the Texas Traffic Institute for states and urban areas rise steadily, especially for very large (e.g., a population of +3 million) and large (e.g., a population of 1 m to 3 m) urban areas. Thus, transportation systems and traffic demand reduction programs have not been successful at reducing traffic congestion in the U.S.